Regulators enhance position on critical software

Seven international regulators have enhanced a common position on their expectations when licensing safety critical software for nuclear reactors. This is highlighted in the latest revision of a consensus document, originally published in 2000.

World Nuclear News has seen a copy of the report, which the UK's Office for Nuclear Regulation (ONR) plans to publish soon.

The ONR and nuclear regulators from Belgium, Canada, Finland, Germany, Spain and Sweden have updated the document to "reflect current expectations and consistent practical standards", an ONR spokesperson said. It is also the first revision to include contributions from the US Nuclear Regulatory Commission. While the US NRC has not endorsed the report for direct regulatory use, the spokesperson said, it has published a separate technical document that contains the report, "recognising it as a valuable reference" for future improvements in its regulatory guidance.

According to the ONR, the document is particularly relevant to new build and generic design assessments as it enables a level playing field across many countries and enables regulators to set consistent requirements. It is used routinely by the regulators concerned and is recommended to nuclear regulators and licensees all over the world, the ONR added.

"It is widely accepted that the assessment of software cannot be limited to verification and testing of the end product, i.e. the computer code," the report says. "Other factors such as the quality of the processes and methods for specifying, designing and coding have an important impact on the implementation." It adds: "Existing standards provide limited guidance on the regulatory and safety assessment of these factors. An undesirable consequence of this situation is that the licensing approaches taken by nuclear safety authorities and by technical support organizations are determined independently and with only limited informal technical coordination and information exchange."

The report is intended to be useful in three main ways. Firstly, to coordinate regulators' and safety experts' technical viewpoints in licensing practices, or design and revision of guidelines. Secondly, as a reference in safety cases and demonstrations of safety of-software based systems. Thirdly, as guidance for manufacturers and major instrumentation and control suppliers on the international market.

The ONR stressed that the report should neither be considered as a standard, nor as a new set of European regulations, nor as a common subset of national regulations, nor as a replacement for national policies. "It is an account," it said, "as complete as possible, of a common technical agreement among regulatory and safety experts."

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by World Nuclear News